The monitor aspects and guides in creating and editing videos

What are the options encapsulated in Program monitor? What are the different Scaling options? What are the available resolutions in Program monitor? What is the use of button editor/ what is Playhead? How important it is in video editing? How can you set the display quality for the source monitor and program monitor? Please provid me more elaborated and compact instructions to resolve this? What are the menus and icons I need to remember to make this happen in my project?

Thank you!